The tremendous variety of baking pans used in commercial baking and the frequent requirement that a single oiler and pan sensor arrangement work with several different pans presents two major challenges. The first is to produce a pattern of sprays which gives a light, evenly distributed coating of release agent only on those portions of the pan which contact the baked product. The second is to consistently synchronize or align the spray pattern with moving pans.
Further, liquid sprayed through nozzles tends to form a very fine mist commonly referred to as "overspray" which does not adhere to the surface of the pan and results in contamination of the atmosphere in the vicinity of the pan or application of oil to surfaces around the pan.
Sequence control apparatus heretofore employed for controlling bakery pan oilers have limited capability for applying precisely controlled quantities of liquid to precisely controlled areas on pan or conveyor band surfaces. Consequently, the systems tend to apply excessive quantities of oil or other materials which detracts from the quality of the resulting food product and requires excessive maintenance and cleaning to operate the systems.
Current systems for the application of oils and other release agents to pans used for commercial baking (commonly referred to as "oilers" or "greasers") provide very limited control of application patterns. Pan sensing is frequently a problem with these systems as well. Consequently, these systems are unable to oil some types of pans and, they give poor results with many other pans. A sequence controller capable of extending the spray pattern capabilities of such systems and adapted to sense the location of a pan without using special sensors is needed.
Commercial pan oilers apply a release agent such as vegetable oil to the baking pan using one or more spray nozzles. The nozzles are usually mounted above a pan conveyor and spray into the pans as they pass below. Most oilers are designed for use with pans that have well defined cavities in a uniform rectangular arrangement. A typical nozzle configuration uses a selected number of nozzles positioned in a row across the pan conveyor. Each nozzle is individually adjusted along a track to match nozzle spacing to the cavity spacing of various pans.
A pan sensor is normally mounted below the conveyor to sense the bottom profile of the pan. When the sensor detects the leading edge of each cavity, it triggers a short spray from all selected nozzles. The position of the spray within each cavity is determined by the position of the pan sensor relative to the nozzle line.
Pan sensor position is usually adjusted to trigger a spray in the center of each cavity. Spray duration is adjusted to control the amount of release agent applied per spray cycle. Since spray tips commonly used give relatively high flow rates, the maximum spray duration is typically less than a tenth of a second and, the pan travels only a few tenths of an inch along the conveyor during the spray cycle. This gives the effect of spraying a single shot or burst of oil into each cavity.
The current systems are limited because they only spray when a signal is received from the pan sensor. This means that a consistently detectable pattern of features must exist on some profile of the pan which exactly matches the desired pattern of sprays.
Most pan sensors in use are either the metal detecting proximity type or the optical proximity type. These sensors are on if they detect a sufficient amount of metal or a sufficient optical path. Because they are either on or off, and because they are only sensitive to a single characteristic of the pan, they are most effective where a high contrast profile exists. Bent pans, which are common in the industry, can cause the sensors to miss sprays. Also, many commercial baking pans have frames, braces, and unusual geometries which will cause misses or extra sprays.